Unlike that laser printer in your office, there is no toner, no paper and no "PC LOAD LETTER" errors.

Instead of ink, these printers — called 3-D printers — use lasers to heat granules of plastic or metal to build up three-dimensional parts, layer by layer. The end product could be any solid design, however complex.

Aerospace manufacturers like Pratt & Whitney and GE Aviation are extending the limits of this technology to make production-run parts for their latest commercial engines. This process is letting manufacturers design components that would have been impossible to mill or forge in yesterday's aerospace factories, while saving money and, in some cases, making parts lighter.

And, for 3-D printing — also called additive manufacturing — the fact that the vanguard technology has passed through the testing fires of a jet engine is a good sign.

Tom Maloney, director of technology research and applications for the Connecticut Center for Advanced Technology, which aids manufacturers who want to use the technology, said, "It's definitely progress … even call it a milestone."

"We've learned a lot about how we should run these machines," he said of 3-D printers. "I'm certainly very bullish that we'll see much more additive technology implemented in this country, but we are also going to see other manufacturing equipment and software continuing to evolve as well."

Pratt, the engine division of Hartford-based United Technologies Corp., put more than two dozen 3-D-printed components on its latest quiet and fuel-efficient PurePower geared turbofan engine, said Thomas Prete, the company's head of engineering. "We've contemplated lots of parts and continue to add to the list."

Pratt's main competitor, GE Aviation, is using 3-D printing to make complex fuel nozzles for an engine.

Prete said that Pratt's designers can now make a single part in one process that otherwise would have been a time-consuming combination of five or 10 pieces that need to be attached and heat-treated before they are ready. That improvement alone saves time and money.

But the main advantage, Prete said, is that engine designers can do things that would have been impossible. "In a basic fabrication," he said, "you sometimes have to make performance trades." For example, engineers can make an initial design that's an A+, but because of manufacturing limitations sometimes only a B- is possible.

With the technology, it's just as easy to make something complex as it is to make something simple. It's like firing up the inkjet to print out a copy of "The Mona Lisa" compared to using it to print a solid color. It doesn't take more time or more ink to print out the one that is significantly more complex.

And a wide, practical view of the technology, to the military, is the ability to print replacement parts, supplies and perhaps even structures for military bases with just a machine and a supply of material, whether plastic or metal. That ability could transform an aircraft carrier into a "floating factory" that could supply replacement parts to a broken tank or an aircraft by processing a data file through an onboard 3-D printer.

Printing Since The '80s

Notwithstanding the new wave of interest, with news of plastic firearms and cranial implants printed from computer files, the 3-D printing narrative at Pratt began in 1988, when the company bought a fleet of 3-D printers for its engineers to design prototype engine parts.

The machines spat out plastic prototypes for testing and development and, once they were deemed to be of optimal design, engineers milled or forged a metal version. In the past four or five years, as technology has advanced, Pratt adopted metal 3-D printing prototyping.

"What we do now is go directly from design to metal using additive manufacturing so you eliminate an entire process," Prete said. The process speeds up the company's engine development as well as saves costs by eliminating the need to mill down new parts every few days.

"What's new here is additive manufacturing of this type is replacing traditional types of subtractive manufacturing," Prete said.

Pratt wouldn't reveal which specific parts were being 3-D printed because the information is proprietary. But Prete could say that some of the 25 parts are simple like brackets and others are more complicated components in the engine's air pathway, a high-temperature and constant-stress area of the engine.

Industrializing the technology to the point that it will withstand the jet engine environment — building confidence in part strength and performance — has been quite the process, experts say. Materials and processes must be unimpeachable and consistent. Costs need to make sense economically, and output needs to keep up with traditional manufacturing methods.